System for emulating an environment for testing a frequency modulated continuous wave (FMCW) detection and ranging (LiDAR) system

ABSTRACT

A system for emulating an over-the-air environment for testing a light detection and ranging (LiDAR) unit under test (UUT). The system may comprise a lens system that receives light from the LiDAR UUT and a plurality of optical processing chains. The system may generate light into free space based on the optical signals processed by each chain. The system may process received light optically to maintain coherence with light received from the LiDAR unit under test and may process all points in a LiDAR image simultaneously. The system may operate to emulate an over-the-air environment for a time-of-flight LiDAR UUT, a frequency modulated continuous wave LiDAR UUT, and/or a flash LiDAR UUT.

PRIORITY CLAIM

This application claims benefit of priority to U.S. provisional patentApplication No. 63/023,984 titled “System for Emulating an Environmentfor Testing a Light Detection and Ranging LiDAR System” and filed on May13, 2020, whose inventors are Marcus daSilva, Amarpal Khanna, JasonMarks, and Douglas Farrell, which is hereby incorporated by reference inits entirety as though fully and completely set forth herein.

FIELD OF THE INVENTION

The present disclosure relates to the field of test, and moreparticularly to a system for emulating an over-the-air environment fortesting a light detection and ranging (LiDAR) system.

DESCRIPTION OF THE RELATED ART

Light Detection and Ranging (LiDAR) is a method for detecting objects,targets, and even whole scenes by shining a light on a target andprocessing the light that is reflected. LiDAR is, in principle, verysimilar to radar. The difference is that LiDAR uses light with awavelength outside the radio or microwave bands to probe the target.Typically, infrared light is used, but other frequencies are alsopossible. The much smaller wavelengths allow LiDAR to have betterspatial resolution, allowing it to represent whole scenes as pointclouds. Unlike a photographic image, which maps intensity and color onto2 dimensions, each point in the LiDAR point cloud may additionally havean associated distance and/or velocity.

A typical LiDAR unit uses lasers to emit light. These emissions arescanned over the field of view and reflected by any objects in theirpath. The reflected light is received and processed by the LiDAR unit.Measurements (amplitude, delay, Doppler shift, etc.) of the receivedlight as well as the scan angle (ϕ, θ) are aggregated, creating aphysical description of the objects in the LiDAR's field of view. Thismethod can represent a scene as a cloud of points as shown in FIG. 1 .Each point in the cloud may have the following attributes:

-   -   Horizontal angle or azimuth (typically denoted by ϕ)    -   Vertical angle or elevation (Typically denoted by θ)    -   Distance from the LiDAR unit. This is typically done by        measuring the delay required for the light to make a round trip        to the object and back.    -   Speed relative to the LiDAR unit. This may be measured in two        ways:        -   Doppler shift of the reflected light.        -   Computing the change in detected distance over successive            distance measurements.    -   Reflectivity. This is the fraction of the incident light that is        reflected by the object, sometimes referred to as “intensity”.

Developers and manufacturers of LiDAR units as well as the makers of thevehicles on which they will be mounted (cars, aircraft, etc.) often needto test the LiDAR under various conditions. Currently, as of 2020,developers and manufacturers resort to either: 1) testing in outdoorenvironments or 2) building a physical model of a real-world environmentin a large area. While this can provide a well-defined test environment,it is large, expensive, difficult to automate and not scalable.

Therefore, improvements in the field are desirable.

SUMMARY OF THE INVENTION

Embodiments are presented herein of a system and method for performingLiDAR test and target emulation. More specifically, embodiments relateto a system for emulating an over-the-air environment for testing and/orcalibrating a light detection and ranging (LiDAR) unit under test. Thesystem may comprise an input lens system configured to receive lightfrom the LiDAR unit under test (UUT), a plurality of optical processingchains coupled to the lens system, and an output lens system coupled toeach of the optical processing chains. In some embodiments, a singlelens system may function as both the input lens system and the outputlens system. The output lens system is configured to generate light intofree space and/or back to the LiDAR UUT based on the optical signalsprocessed by each optical processing chain.

Each of the optical processing chains may comprise at least one opticalfiber coupled to the input lens system and configured to provide opticalsignals corresponding to the received light. Each chain may alsocomprise a frequency shift emulator coupled to the plurality of opticalfibers which is configured to create a frequency offset in the receivedoptical signals. The frequency shift emulator may include an optical IQmodulator or an optical phase-locked loop. In some embodiments, thefrequency shift emulator may use a different frequency shift forup-slope and down-slope to emulate both distance and Doppler shift. Eachchain may further comprise a selectable optical delay device coupled tothe frequency shift estimator and configured to selectively delay theoptical signals to emulate a round-trip delay of reflected light.Finally, each chain may comprise at least one opticalattenuator/amplifier configured to selectively control (attenuate oramplify) the amplitude of the optical signals to emulate differentlevels of reflectivity and path loss.

The system may be configured to process received light optically tomaintain coherence with light received from the LiDAR unit under test.In some embodiments, the system may process all points in a LiDAR imagesimultaneously.

The system may also comprise a LiDAR image generator coupled to thefrequency shift emulator, the selectable optical delay and the opticalattenuator/amplifier, which may be user programmable to controloperation of these devices. For example, the LiDAR image generator maybe configured to provide a frequency shift value to the frequency shiftemulator for use by the frequency shift emulator in creating a frequencyoffset in the received optical signals. The LiDAR image generator mayalso be configured to provide a delay value to the selectable opticaldelay for use by the selectable optical delay to delay the opticalsignals to emulate the round-trip time of the reflected light. Finally,the LiDAR image generator may be configured to provide an amplitudevalue to the optical attenuator/amplifier for use in controlling theamplitude of the optical signals to emulate different levels ofreflectivity, polarization change, and path loss from free space,spectral components of the reflection, and/or diffuse components of thereflection. The LiDAR image generator may be configured to provide thefrequency shift value, the delay value, and/or the amplitude value foreach point in a point cloud generated by the system. The set of valuesprovided by the LiDAR image generator may correspond to a particulartest environment. In other words, the set of values may bepre-calculated to emulate a particular scene for testing the LiDAR UUT.

Embodiments may also relate to a system for emulating an over-the-airenvironment for testing a LiDAR UUT. The system may comprise an inputlens system configured to receive light from the UUT. The system mayfurther comprise an input optical splitting block coupled to the inputlens system and configured to receive optical signals and provideportions of the optical signals to one or both of a first opticalprocessing path and a second optical processing path. The system mayalso comprise at least one optical shutter array coupled to the firstoptical processing path and the second optical processing path.

The first optical processing path may comprise an array ofphotodetectors for determining angles of the laser pulse at a particularinstant in time, wherein a location of received light on thephotodetector array is used to open a corresponding element in theoptical shutter array. A location of received light on the photodetectorarray may correspond to a vertical and horizontal scanning angle (ϕ,θ),wherein the vertical and horizontal scanning angle is used to open acorresponding element in the optical shutter array, or alternatively, asingle lens system may be used to both receive the light from the LiDARUUT and output the processed light back to the LiDAR UUT. In oneembodiment, each photodetector in the array of photodetectors has aone-to-one mapping with a corresponding shutter in the optical shutterarray. Alternatively, each of a plurality of sets of pluralphotodetectors in the array of photodetectors may have a many-to-one ora one-to-many mapping with a corresponding shutter in the opticalshutter array.

The second optical processing path may comprise an amplitude controllerto control the amplitude of the optical signals to emulate differentlevels of reflectivity, polarization change, and path loss from freespace, spectral components of the reflection, and/or diffuse componentsof the reflection. The second path may also comprise a LiDAR imagegenerator coupled to control the amplitude controller. The secondoptical processing path may be configured to provide an attenuatedsignal to the optical shutter array for exit through one or more openelements in the optical shutter array.

In some embodiments, the second optical processing path furthercomprises a frequency shifter coupled to the selectable optical delayelement. The frequency shifter is configured to create a frequencyoffset in the received optical signals. Thus, in this embodiment thesecond optical processing path may provide a frequency shifted andattenuated signal to the output of the system. For example, the systemmay include an optical shutter array, and the processed signal may beprovided for exit through one or more open elements in the opticalshutter array. Alternatively, the system may utilize a lens system toboth receive the light from the LiDAR UUT and output the processed lightback to the LiDAR UUT. The frequency shifter may comprise an optical IQmodulator or an optical phase-locked loop.

In some embodiments, the second optical processing path may furthercomprise a selectable optical delay element coupled to the frequencyshifter. The selectable optical delay element may be configured toselectively delay the optical signals to emulate a round-trip delay ofreflected light. In this embodiment, the second optical processing pathmay be configured to provide a delayed and attenuated signal to the atleast one optical shutter array for exit through one or more openelements in the optical shutter array. Alternatively, the system mayutilize a lens system to both receive the light from the LiDAR UUT andoutput the delayed and attenuated signal back to the LiDAR UUT.

Other aspects of the present invention will become apparent withreference to the drawings and detailed description of the drawings thatfollow.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when thefollowing detailed description of the preferred embodiment is consideredin conjunction with the following drawings, in which:

FIG. 1 shows pulsed time-of-flight (ToF) LiDAR operation, according tosome embodiments;

FIG. 2 is a block diagram of a frequency modulated continuous wave(FMCW) LiDAR system, according to some embodiments;

FIG. 3 shows an up-down linear frequency modulation (FM) ramp, accordingto some embodiments;

FIG. 4A shows single-flash LiDAR operation, according to someembodiments;

FIG. 4B shows multi-flash LiDAR operation, according to someembodiments;

FIG. 5 illustrates a block diagram of a ToF LiDAR target emulator,according to some embodiments;

FIG. 6 illustrates a LiDAR scene emulator that can work for ToF, FMCW,and flash LiDARs, according to some embodiments;

FIG. 7 illustrates block diagrams of systems for creating an opticalfrequency shift, according to some embodiments;

FIG. 8A is a block diagram of a LiDAR scene emulator for ToF and FMCWLiDARs including an optical shutter array, according to someembodiments;

FIG. 8B is a block diagram of a LiDAR scene emulator for ToF and FMCWLiDARs including an input/output lens system, according to someembodiments;

FIG. 9A illustrates one-to-one mapping between a photodetector array andan optical shutter array according to some embodiments;

FIG. 9B illustrates four-to-one mapping between a photodetector arrayand an optical shutter array according to some embodiments;

FIG. 10 illustrates using frequency shift used to emulate both delay andDoppler shift in a FMCW LiDAR, according to some embodiments;

FIG. 11 illustrates a schematic diagram of a flash LiDAR scene emulator,according to some embodiments;

FIG. 12 illustrates a method for utilizing a sequence of 2D matrices toemulate a flash LiDAR over-the-air scene, according to some embodiments;

FIG. 13 illustrates an method for generating an emulated scene for flashLiDAR using dedicated timing elements, according to some embodiments;

FIG. 14 is a flowchart diagram illustrating a method for an emulatorsystem to emulate an over-the-air environment for testing a ToF and/orFMCW LiDAR UUT, according to various embodiments; and

FIG. 15 is a flowchart diagram illustrating a method for emulating anover-the-air environment for a flash LiDAR UUT, according to someembodiments.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and are herein described in detail. It should beunderstood, however, that the drawings and detailed description theretoare not intended to limit the invention to the particular formdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Terms

The following is a glossary of terms that may appear in the presentdisclosure:

Memory Medium—Any of various types of non-transitory memory devices orstorage devices. The term “memory medium” is intended to include aninstallation medium, e.g., a CD-ROM, floppy disks, or tape device; acomputer system memory or random access memory such as DRAM, DDR RAM,SRAM, EDO RAM, Rambus RAM, etc.; a non-volatile memory such as a Flash,magnetic media, e.g., a hard drive, or optical storage; registers, orother similar types of memory elements, etc. The memory medium maycomprise other types of non-transitory memory as well or combinationsthereof. In addition, the memory medium may be located in a firstcomputer system in which the programs are executed, or may be located ina second different computer system which connects to the first computersystem over a network, such as the Internet. In the latter instance, thesecond computer system may provide program instructions to the firstcomputer system for execution. The term “memory medium” may include twoor more memory mediums which may reside in different locations, e.g., indifferent computer systems that are connected over a network. The memorymedium may store program instructions (e.g., embodied as computerprograms) that may be executed by one or more processors.

Computer System (or Computer)—any of various types of computing orprocessing systems, including a personal computer system (PC), mainframecomputer system, workstation, network appliance, Internet appliance,personal digital assistant (PDA), television system, grid computingsystem, or other device or combinations of devices. In general, the term“computer system” may be broadly defined to encompass any device (orcombination of devices) having at least one processor that executesinstructions from a memory medium.

Processing Element (or Processor)—refers to various elements orcombinations of elements that are capable of performing a function in adevice, e.g., in a user equipment device or in a cellular networkdevice. Processing elements may include, for example: processors andassociated memory, portions or circuits of individual processor cores,entire processor cores, processor arrays, circuits such as an ASIC(Application Specific Integrated Circuit), programmable hardwareelements such as a field programmable gate array (FPGA), as well any ofvarious combinations of the above.

Configured to—Various components may be described as “configured to”perform a task or tasks. In such contexts, “configured to” is a broadrecitation generally meaning “having structure that” performs the taskor tasks during operation. As such, the component can be configured toperform the task even when the component is not currently performingthat task (e.g., a set of electrical conductors may be configured toelectrically connect a module to another module, even when the twomodules are not connected). In some contexts, “configured to” may be abroad recitation of structure generally meaning “having circuitry that”performs the task or tasks during operation. As such, the component canbe configured to perform the task even when the component is notcurrently on. In general, the circuitry that forms the structurecorresponding to “configured to” may include hardware circuits.

Various components may be described as performing a task or tasks, forconvenience in the description. Such descriptions should be interpretedas including the phrase “configured to.” Reciting a component that isconfigured to perform one or more tasks is expressly intended not toinvoke 35 U.S.C. § 112, paragraph six, interpretation for thatcomponent.

Embodiments described herein relate to systems and methods for emulatingthe optical environment observed by a LiDAR. More specifically,embodiments described herein may provide developers and manufacturers ofLiDAR units a means to emulate the optical environment observed by aLiDAR that is small, easy to replicate, and controllable by a computer.

There are three prevailing types of LiDAR commercially available or indevelopment in 2020. Each comes with its own emulation challenges: 1)Pulsed Time-of-flight LiDARs (ToF); 2) LiDARS that use a series oflinear FM Chirps, or Frequency Modulation Continuous Wave (FMCW); and 3)Flash LiDARs. Embodiments herein present systems and methods foremulating the optical environment for one or more of these types ofLiDAR, or potentially for other types of LiDAR that may be developed inthe future.

FIG. 1 —ToF LiDAR Block Diagram

FIG. 1 shows a simplified schematic of a ToF LiDAR. The ToF LiDAR usesthe following basic functional blocks to render a scene:

1). Pulsed laser: A ToF LiDAR emits a short-duration, high amplitudelaser pulse. The amplitude may be high in order for the receiver to beable to capture pulses reflected from far away. This need for verystrong light pulses is one of the drawbacks of the ToF LiDAR.

2). Scanner: The laser pulse passes through a scanner that varies theangle with which the light travels over the field of view. Successivelaser pulses are scanned over the scene, covering the field of view.Some LiDARs use a single laser with a 2-dimensional raster scanner,while others may use a vertical array of lasers which are scannedhorizontally (i.e., each laser scans in one dimension). Scanners may bemechanical with rotating mirrors and/or they may be implemented with anarray of solid state lasers, with MEMS devices or optical phase arrays,among other possibilities.

3). Target objects in the field of view. The laser pulses reflect fromtarget objects. The material, roughness and angle of the reflectingsurface determines the reflectivity, or fraction of optical power, thatis reflected. The LiDAR unit will receive a signal that is attenuated bythe reflectivity, polarization change, and path loss from free space,spectral components of the reflection, and/or diffuse components of thereflection. This path loss may be determined by the distance as well asby any impairments such as dust, fog, etc. The reflection, as receivedby the LiDAR, will have a time delay. This delay is the time that lighttakes to make the round trip from the Lidar unit to the target and back.Velocity may be computed from the change in this distance over time fromsuccessive laser pulses. ToF LiDARs do not measure Doppler shift. TheLiDAR unit has information about the angle (ϕ, θ) with which the lightwas transmitted from the scanner settings. The LiDAR uses this angleinformation to reconstruct the scene in its field of view.

4). Point Cloud. The scene is rendered as an array of points, each withthe attributes of: i) The horizontal and vertical angles (ϕ, θ) of theilluminated point relative to the LiDAR; ii) The reflectivity at thepoint illuminated by the LiDAR; iii) The distance between theilluminated point and the LiDAR; and/or 4) The relative velocity of theof the point illuminated by the LiDAR. It is noted that in ToF LiDARsvelocity is only measured indirectly. ToF LiDARs that are commerciallyavailable or in development as of April 2020 may render scenes as pointclouds with 1,000 to 100,000 points.

FIG. 2 : FMCW LiDAR

FIG. 2 shows a simplified schematic of a FMCW LiDAR system. FMCW LiDARuses linear FM modulation of the laser light and synchronous processingat the receiver. Not only are FMCW LiDARs much more resistant tointerference than their ToF counterparts, but they require much lesspeak optical power to have the same range and sensitivity. FMCW LiDARtypically uses an eye-safe wavelength to operate within, since thelasers are always on during operation.

The FMCW LiDAR may use the following basic functional blocks to render ascene:

1) FM Modulated laser source. The Laser in a FMCW LiDAR also produceslight pulses. The pulses, however, are of longer duration and loweramplitude compared to those for ToF LiDARs and they are FM-modulatedwith a linear ramp or frequency sweep. Many FMCW LiDARs use acombination of linear up-ramp and a linear down-ramp in the frequencysweep. The linear frequency sweeps allow several signal processingadvantages over ToF LiDARs, as explained in greater detail below.

2). Linear frequency sweep processing. The linear frequency sweep meansthat the actual frequency of the laser changes linearly in time. Thelaser is reflected by a target object and experiences a round-trip timedelay. This time delay means that the frequency of the received signalis the same as the frequency that was transmitted at an earlier time,before the time delay. The received signal is mixed with the transmittedsignal and the resulting baseband signal is processed electronically.Up-sweep refers to where the received frequency is lower than thetransmitted frequency for a stationary object. Down-sweep refers towhere the received frequency is higher than the transmitted frequencyfor a stationary object. If the target object is moving relative to theLiDAR unit then the received signal also experiences a frequency shiftdue to the Doppler effect, which is independent of sweep direction. Theeffects of transit delay and the Doppler shift can be separated byprocessing the up and down sweeps together. The frequency shift in theup-sweep contains the effect of Doppler minus the effect of the delay.The frequency shift in the down-sweep contains the effect of Dopplerplus the effect of delay.

${\frac{{\Delta f_{up}} + {\Delta f_{down}}}{2} = \Delta_{Doppler}}{\frac{{\Delta f_{up}} + {\Delta f_{down}}}{2} = \Delta_{transit}}$

Accordingly, the effect of the Doppler shift may be separated from theeffect of the round-trip time delay, such that the FMCW LiDAR system maycalculate both the velocity of and the distance to the reflective pointin the scene.

FIG. 3 : Up-Down Linear FM Ramp

FIG. 3 shows a graph of the transmit (TX) and receive (RX) frequency vs.time of an actual LiDAR signal. The frequency may be modulated with alinear ramp. Each chirp ramp (i.e., the up-ramp and the down-ramp) mayhave a time duration longer than the maximum round trip delay. Thereceived signal may be a delayed version of the transmitted signal. Inthe up-ramp, the delay causes the RX frequency to be lower than the TXfrequency. In the down ramp, the delay causes the RX frequency to behigher than the TX frequency. Speed may also cause a frequency shift dueto the Doppler effect. For example, frequency shifts up when the targetis approaching and frequency shifts lower when the target is receding.

Both transit time and the Doppler effect may create a frequency shift.This frequency shift is recovered when the received light pulse is mixedwith the transmitted light pulse.

${{{Up} - {Chirp}:\Delta f_{up}} = {\Delta_{Dop{pler}} - \Delta_{{trans}it}}}{{{Down} - {Chirp}:\Delta f_{down}} = {\Delta_{Doppler} + \Delta_{{trans}it}}}{\frac{{\Delta f_{up}} + {\Delta f_{down}}}{2} = \Delta_{Doppler}}{\frac{{\Delta f_{up}} + {\Delta f_{down}}}{2} = \Delta_{transit}}$

There may be a dead time at the beginning of each up or down ramp whilethe light travels to the target and back.

The scanner may operate as follows. The laser pulse may pass through ascanner that may vary the angle with which the light travels over thefield of view. Successive laser pulses may be scanned over the scene,covering the field of view. Some LiDARs may use a single laser with a2-dimensional scanner, while others may use a vertical array of laserswhich are scanned horizontally (or a horizontal array of lasers whichare scanned vertically). Scanners may be mechanical, with rotatingmirrors or solid state. Target objects in the field of view may affectthe system as follows. The laser pulses reflect from target objects,where the material, roughness and/or angle of the reflecting surfacedetermines the reflectivity, or what fraction of the light is reflected.The LiDAR unit may receive a signal that is attenuated by thereflectivity, polarization change, and path loss from free space,spectral components of the reflection, and/or diffuse components of thereflection. This path loss may be determined by the distance as well asby any impairments such as dust, fog, etc. The reflection, as receivedby the LiDAR will have a time delay. This delay is the time that lighttakes to make the round trip from the Lidar unit to the target and back.The time delay may manifest itself as a frequency shift of the RXfrequency relative to the TX frequency. This shift is negative forup-sweeps and positive for down sweeps. The reflection may also have aDoppler shift which is proportional to the velocity difference betweenthe LiDAR unit and the target object. The Doppler shift may not bedependent on the sweep direction. The LiDAR unit has information aboutthe angles (ϕ, θ) with which the light was transmitted from the scannersettings. The LiDAR uses this angle information to reconstruct the scenein its field of view.

The synchronous receiver may operate as follows. The LiDAR receivercombines the reflected pulse and the transmitted pulse. The result is asignal that may be used to determine the frequency difference betweenthe transmitted and received light at a given instant in time. Thislow-frequency signal (typically in the MHz range) is processed usingconventional RF signal processing techniques. The ability to process thereceived signal electronically, with a much lower bandwidth, may providea large improvement in the achievable signal-to-noise ratio (SNR). Thismay allow distant objects to be imaged with much lower transmit laserpower than what is required with a ToF LiDAR. The relative velocity ofthe target object may be measured directly through the Doppler shift.

Point Cloud. The scene may be rendered as an array of points, each withthe attributes of: 1) The horizontal and vertical angles (ϕ, θ); 2). Thereflectivity of the at the point illuminated by the LiDAR; 3) Thedistance between the illuminated point and the LiDAR; and 4) Therelative velocity of the of the point illuminated by the LiDAR.

FMCW LiDARs in development as of April 2020 can render scenes as cloudswith 1000 to 100000 points.

Flash LiDAR

Flash LiDAR is a specific type of LiDAR, as opposed to Scanned PulsedTime of Flight (“ToF”) and Frequency Modulated Continuous Wave (“FMCW”)LiDAR types. Flash LiDAR devices are currently commercially available,and the technology is continuously improving. Some embodiments hereinaddress the challenge of testing Flash LiDAR devices through amethodology that allows for a LiDAR device to be coupled to a systemthat emulates a 3D world environment. This process works by emulating aresponse that a Flash LiDAR would receive in a driving scenario or othercontrived scenario through a combination of optical and electricaltechnology. The response that the LiDAR receives will then create a“point cloud,” which is the standard output for a Flash LiDAR device,that will be substantially similar to the point cloud that would becreated in a real driving or other scenario. Because the Flash LiDARoptical output is not physically connected to the emulation system, theemulation will occur optically “over the air,” or within free space.This methodology will enable the test of Flash LiDAR in a costeffective, efficient, and highly repeatable way.

FIG. 4A illustrates a simplified schematic of a Flash LiDAR device witha single laser source. Flash LiDAR, as the name implies, behaves muchlike the familiar flash camera. The entire scene is flooded with light.The Flash LiDAR differs from others in the following ways. First, thereis often no scanner associated with the transmitted light pulses. For asingle laser Flash LiDAR, the light from a single laser pulse is spreadover the entire field of view with a system of lenses or a diffuser. Forsome flash LiDAR devices, scanning systems may be utilized, though theystill differ from ToF and FMCW scanned systems in that they are“flashing” a subsection of the field of view at a time and thatsubsection is moved over time. Target objects reflect the flash oflight. Unlike the point-by-point illumination of other types of LiDAR,the entire scene (or a subsection of the scene) is illuminated at once,by flashing a short laser pulse and using a diffuser to spread thelight. Second, the reflected light is captured by a lens and projectedonto an imager much like an electronic camera. Third, the imager,composed of thousands of pixels, processes each pixel using ToF, FMCW orother techniques to render an image.

FIG. 4B shows a simplified schematic of a multi-beam flash LiDAR.Multi-beam flash LiDAR is similar to single-beam flash LiDAR, butdiffers from single-beam flash LiDAR in that more than one laser (e.g.,potentially an array of lasers) is used on the transmitting side of theLiDAR. Each laser in the array illuminates a small part of the targetarea, and firing of the lasers is individually controlled. In someembodiments, a few lasers may be fired at a time, and a full image isbuilt up once all lasers have fired. In some embodiments, firing may befoveated with higher frequency firing in regions deemed more important.Advantageously, the range limitations of flash LiDAR may be mitigated bymulti-beam flash LiDAR, as it reduces the power required for the lasersbecause each laser illuminates a small area.

Some embodiments herein describe over-the-air environment emulatorsystems to operate with single and/or multi-beam flash LiDAR devices.

LiDAR Scene Emulation Challenges

The job of a LiDAR scene emulator is to create an emulated over-the-airenvironment that is, to the LiDAR under test (LUT), indistinguishablefrom an actual scene. Additionally, it is desirable for the sceneemulator to be small, inexpensive and programmatically controlled,allowing for the emulation of many moving objects, impairments(sunlight, dust, snow, other LiDARs, etc), and environments. Someattributes of a LiDAR emulator include:

1) The Field of view (FOV), i.e., the horizontal and vertical (ϕ, θ)angle over which a LiDAR creates an image. The symbol ϕ represents thehorizontal angle range, which may range from 30 to 360 degrees forAutomotive LiDAR applications. The symbol θ represents the verticalangle, which may vary in various ranges, e.g., from −10 to +80 degrees,from 10 to 90 degrees, etc., for automotive LiDAR applications. Anemulator may create scenes covering all or a part of the FOV.

2). The Angular resolution, which is the is the smallest angle that aLiDAR can detect. The vertical and horizontal angular resolutions may beof the order of 0.1 degrees, as one example.

3). Number of points in the point cloud. Automotive LiDARs typicallydepict scenes with 1,000 to over 1,000,000 points, although othernumbers of points are also possible.

4). Minimum/maximum distance. Automotive LiDARs may function fordistances of 1 m to about 300 m, among other possibilities.

Minimum/maximum velocity of emulated objects. Automotive LiDARs maymeasure speeds ranging from 0 to 500 km/hour.

5). Interference generation, such as noise, dust, rain, sunlight, otherlidars, etc.

6). Scene dynamics. The ability to change a scene from frame to frame.LiDARs may have frame rates of 10 to 100 frames per second.

7) LiDAR Types. The phrase “LiDAR Types” refers to the type of LiDARthat the system can emulate. Currently, commercial emulators exist forToF LiDARs. FMCW and flash LiDARs are now under development in 2021.There is an industry demand for a programmable emulator that works withFMCW LiDARs.

8) Emulator Size. Automotive LiDARs are designed to see a large field ofview over distances as large as 300 meters. Other LiDAR applications mayreach even farther. The ideal emulator occupies a small fraction of thisspace, allowing it to be placed on a bench, factory floor, or on aproduction line.

9). Point cloud emulation. LiDARs may render a scene with 1000 to 100000points. Each point in the point cloud has the azimuth and elevationangles, reflectivity, distance and Doppler shift. Scanning LiDARs maytake advantage of sequential nature of a scan to time share theelectronic and optical processing elements.

10). Flash LiDARs flood all points in a scene with light simultaneously.Optical processing is done in parallel. Like camera imagers, the imagerin a Flash LiDAR receiver may use a scanning process internally. Unlikethe TOF and FMCW systems that use laser scanning for transmission, thereis no way to know the state of the scanner from observations of theexternal laser pattern. Knowledge of this internal scan, if available,may be used to share optical and electrical signal processing componentsin an emulator.

Commercially available automotive LiDAR emulators currently in existenceare designed for scanned pulsed ToF Lidars, and cannot be used withFlash or FMCW types. These emulators work using the approach illustratedin FIG. 5 . Embodiments herein improve on these LiDAR emulators byproviding systems and methods for LiDAR emulation that may be used withFMCW and/or Flash LiDAR systems.

FIG. 5 : Scanned ToF LiDAR Target Emulator Block Diagram

FIG. 5 is a block description of a prior art ToF target emulator. Anarray of photodetectors in conjunction with a system of lenses ormirrors is used to detect a light pulse from the LiDAR UUT. Eachlocation on the photodetector array (i.e., each pixel) corresponds to adistinct vertical and horizontal scanning angle (ϕ, θ). An alternativemethod is to ignore the transmitted laser and use a signal from theLiDAR unit to determine the state of the scanner and the timing of thelaser pulse. Each photodetector in the photodetector array is connectedto a pulse generator. The rising edge from the photodetector triggersthe pulse. An image processor is programmed to assign an amplitude and adelay value to each pixel. The delay and amplitude values are fed to adelay generator and amplitude controller. The delayed andamplitude-scaled pulses are fed to an array of laser diodes. Thesegenerate a pulse of light that has been scaled and delayed. The array oflaser diodes can have a one-to-one correspondence with the photodetectorarray. The number of laser diodes may not need to have a one-to onecorrespondence with the photodetector array. The UUT has knowledge ofangles through which the original pulse was sent and may not need a fullresolution laser diode array to reconstruct a scene. An importantdistinction between the LiDAR emulator shown in FIG. 5 and someembodiments described herein is that the emulator in FIG. 5 creates newlight pulses responsive to receiving light pulses from the LiDAR UUT,whereas LiDAR emulators based on some embodiments described hereinmodulate the received light pulses and return them to the LiDAR UUT.

Emulation System Embodiments

The novel emulator described herein may have various embodiments. Insome embodiments, the emulator described herein may provide LiDAR sceneemulation for more than one type of LiDAR, including all three of ToF,FMCW and Flash. This method, while plausible, may be too complex andexpensive for practical implementation using currently availabletechnology. Technology advances may make this approach feasible in thefuture. A second embodiment may be a less complex concept for LiDARscene emulation that may be used for both ToF and FMCW LiDARs. Otherembodiments may be a version that may be used for only one of ToFLiDARs, FMCW LiDARs, or Flash LiDARs.

The following description begins with the most general, complex andexpensive implementation. Simplifications that are made possible due tothe properties of ToF and FMCW LiDARs are described further below.

FIG. 6 —Parallel Point Cloud Emulator—LiDAR Scene Emulator

FIG. 6 is a conceptual block diagram of a LiDAR target emulator that isagnostic to LiDAR type. In other words, FIG. 6 illustrates a parallelpoint cloud emulator-LiDAR scene emulator that may work for ToF, FMCWand Flash LiDAR UUTs. This emulator embodiment can process all points ina LiDAR image simultaneously. This emulator embodiment may also processthe laser light optically, maintaining coherence with the originalsignal transmitted by the LiDAR UUT. This coherence may be useful forFMCW processing.

The following provides Parallel Point cloud emulator block descriptions:

The input optical processing block may contain an array of lensescapable of guiding each point in the LiDAR cloud into a correspondingoptical fiber, each connected to an optical processing chain. There ismapping of optical fiber and processing chains to each point in thecloud. Some embodiments may employ direct mapping where a LiDAR thatrenders scenes with 1000 points would require 1000 optical processingchains, one per point. Other embodiments may employ indirect mappingwhere multiple points may map into each optical processing chain.

Each optical processing chain may contain a frequency shift emulator,which may also be referred to as a Doppler shift emulator. The Dopplershift emulator creates a frequency offset in the light conducted by thefiber. This can be done in several ways as shown in the block diagramsshown in FIG. 7 .

Optical in-phase quadrature (IQ) modulator. An IQ modulator can be usedto shift the frequency of an incoming signal. Optical IQ modulators haveoptical bandwidths in the range of 10's of GHz and optical localoscillator (LO) inputs in the optical wavelengths used by LiDARs. An RFsignal generator can be used to generate a sine wave and a cosine waveat the same frequency. The cosine wave is fed to the I input and thesine wave to the Q input of the IQ modulator, such that I=Cos (ωt) andQ=−sin (ωt). The optical signal at the output of the IQ modulator willbe shifted by the angular frequency ω. The frequency ω may be chosen tocorrespond to the Doppler shift for the point being emulated. Analternative to the optical IQ modulator is to use an opticalPhase-locked-loop (PLL) to provide the frequency shift as seen in FIG. 7. More particularly, FIG. 7 illustrates methods for creating an opticalfrequency shift, including either an optical IQ modulator or an opticalPLL. It is noted that ToF LiDARs cannot detect Doppler shift, and thisblock may not be used for ToF LiDAR emulators.

Each optical processing chain may also contain a selectable opticaldelay. The selectable optical delay may operate to delay the opticalpulse to emulate the round-trip delay of the reflected laser light. Thismay be implemented as a switchable segment of binary weighted delays.Time segments such as 2, 4, 8, 16, 32, 64, 128, 256, and 512 ns segmentscan emulate round trip delays corresponding to, e.g., 30 cm to 76.8 m.The delays are often implemented as selectable lengths of optical fiber.

Each optical processing chain may also contain optical attenuators andamplifiers: These provide a means of controlling the amplitude of theoptical signals to emulate different levels of reflectivity,polarization change, and path loss from free space, spectral componentsof the reflection, and/or diffuse components of the reflection. Thelight traveling through each of the optical fibers can selectively beattenuated or amplified to ensure that the light intensity received bythe LiDAR corresponds to the reflectivity and path loss at the locationon the object being emulated.

This method has numerous advantages, such as that it works for all typesof LiDAR, independent of scanning method, modulation or imagingapproach. Also, this method truly emulates the behavior of real objects.Disadvantages of this method include complexity, size and power, whichmay render this method impractical for more point clouds with manypoints. Further, this method may use an RF generator, IQ modulator, andselectable optical delay for each point in the cloud. These areexpensive and large, as clouds can have up to 100,000 points, and hencecosts can run into the $10s of millions at the present time. It is notedthat advances in technology (photonic ICs, multilane parallel fibers . .. ) will likely make this more economically feasible in the future.

FIGS. 8A-B: Emulator System for Pulsed ToF and FMCW LiDARs.

FIGS. 8A and 8B illustrate two LiDAR scene emulators that may work forboth FMCW and ToF LiDAR UUTs, according to some embodiments. Moreparticularly, FIG. 8A illustrates a point cloud emulator for scanned,pulsed systems, e.g., a LiDAR scene emulator for ToF and FMCW LiDARs.This system uses the fact that the laser is scanned and that laserpulses do not arrive at all points in a point cloud simultaneously. Thisallows the expensive optical and electronic signal processing blocks tobe time-shared. The light pulses from the LiDAR under test are processedoptically, maintaining the coherence needed by FMCW LiDARs.

FIG. 8A illustrates a schematic block diagram for a LiDAR scene emulatorcapable of FMCW and ToF LiDAR scene emulation. The system may include aninput optical splitting block 802 that takes a portion of the incomingoptical signal and splits it into two paths. Path 1 is fed to an arrayof photodetectors for determining the angles (ϕ, θ) of the laser pulseat a particular instant in time. Path 2 is fed to a lens system 804 thatfocuses all the light into a small number of optical fibers, eachfeeding an optical processing chain. LiDARs that have a single laser anda two-dimensional scan may use a single optical processing chain. LiDARsthat have multiple lasers and a one-dimensional scan may use one opticalprocessing chain for each laser in the LiDAR under test. For example, aLiDAR with a vertical stack of 16 lasers may use 16 optical processingchains.

In Path 1, the array of photodetectors in conjunction with a system oflenses or mirrors is used to detect a light pulse from the LiDAR UUT.The location on the photodetector array (pixel) corresponds to thevertical and horizontal scanning angle (ϕ, θ). This information is usedto open a corresponding element in an optical shutter array 806 asillustrated in FIGS. 9A and 9B. The photodetector array and the opticalshutter array can have a one-to-one mapping as shown in FIG. 9A or adifferent mapping scheme as illustrated in FIG. 9B. The photodetectorarray determines which of its detectors has a light pulse. There is amapping from the photodetector array to the optical shutter array. Thismay be a one-to-one mapping, such as in FIG. 9A, or other possiblemapping schemes may be used, such as shown in FIG. 9B, which illustratesa 1:4 mapping. As shown in FIG. 9B, the proportion of light in each ofthe 4 elements in the top left quadrant of the photodetector array maybe used to identify the center of the laser spot for the optical shutterarray. Other mappings are also possible. Each photodetector in the arrayhas a corresponding pulse generator. The rising edge from thephotodetector triggers the pulse. This pulse may be fed to a LiDAR imagegenerator as a timing reference.

Path 2 may comprise an optical processing chain. As shown, light pulsesfrom the optical signal splitter are fed into an optical processingchain comprising a frequency shifter, a selectable optical delay, anamplitude controller, and a LiDAR image generator. The LiDAR imagegenerator may be programmed to assign an amplitude, a Doppler shift anda delay value to each point in the point cloud. The delay value for thepoint(s) activated in at each scan position is (are) fed to a selectableoptical delay. The Doppler shift frequency for the point(s) activated inat each scan position is (are) fed to a RF signal generator feeding anoptical IQ modulator. The IQ modulator may create an offset in theoptical frequency equal to the desired Doppler shift. An optical PLL canalso be used to generate a frequency offset. The amplitude value for thepoint(s) activated in at each scan position is (are) fed to a selectablegain/attenuation stage. The light signal from each optical processingchain is fed to a lens system that illuminates an optical shutter array806.

The delayed, Doppler shifted and attenuated signal exits through theopen elements in the optical shutter array. A mapping exists between thephotodetector array and the optical shutter array. Optical shutterarrays can be reflective (mirrors) or transmissive (lenses).

FIG. 8B illustrates a LiDAR scene emulator system that operates similarin some respects to the system shown in FIG. 8A. However, in the systemshown in FIG. 8B, a lens system 854 is used to both receive the lightfrom the LiDAR UUT and output the processed light back to the LiDAR UUT(rather than using a separate optical shutter array or MEMS mirror arrayfor output as in FIG. 8A). As illustrated in FIG. 8B, an applicationspecific device such as the illustrated off-axis parabolic mirror 852may be used to direct the light from the LiDAR UUT onto a lens system854. The lens system 854 focuses different points of light received fromthe LiDAR UUT onto different optical fibers (or optical circulators)855. A beam splitter is also utilized to split the received light intoPath 1 and Path 2, as in FIG. 8A. The light on Path 2 is fed to a scandetection system 874. Scanning information may (optionally) be receivedfrom the LiDAR UUT. The received light and/or the scanning informationis then utilized by an amplitude controller 870, and optical attenuator866, an optical amplifier 868, a LiDAR image generator 864, and/or an RFsignal generator 862 to determine the parameters of the opticalmodulator 858 and selectable optical delay 860 to modify the light onPath 1 to emulate the over-the-air environment. Subsequent to processingthe received light by an optical modulator 858 and a selectable opticaldelay 860 in each of the optical fibers, the processed light is returnedto the optical fibers for transmission back through the lens system andto the LiDAR UUT.

Another embodiment relates to a point cloud emulator for scanned, pulsedToF LiDAR Systems. Pulsed ToF systems do not directly respond to Dopplershifts. In the systems of FIGS. 8A-B, the frequency shifter block may beunnecessary and may be removed. The LiDAR image generator block may beagile and accurate enough to change delay from point-to-point and fromframe-to-frame in a way that accurately reflects the desired targetvelocity.

Another embodiment relates to a point cloud emulator for scanned FMCWLiDAR Systems. FMCW LiDARs experience both path delay and Doppler shiftsas a frequency shift. In some embodiments, the selectable delayapparatus from the diagrams in FIGS. 8A-B may be removed, and both pathdelay and Doppler shift may be emulated by the IQ frequency modulator.This may operate in a dual slope FMCW LiDAR system as follows. The RFsignal generator in FIG. 7 may be designed to be able to changefrequency quickly as the FMCW slope changes from positive to negative asshown in FIG. 10 . During the up-slope, the RF Signal Generator may beprogrammed to produce a frequency that has the Doppler component minusthe delay component. During the down-slope the RF Signal Generator maybe programmed to produce a frequency that has the Doppler component plusthe delay component. There may be a switching transient in the signalgenerator. This transient is ignored as long as it happens during theshort time when the LiDAR switches from up-slope to down-slopeprocessing. This dead time may be at least the round-trip delay for thelight pulses, and may be approximately 6 ns per meter of distance. Thisdead time may allow for the frequency to be changed.

Flash LiDAR Scene Emulation

In some embodiments, a LiDAR scene emulator system is describedspecifically for flash LiDAR, both for single-beam flash LiDAR andmulti-beam flash LiDAR. These methodologies may allow for LiDAR test,emulation, and calibration, for both the full field of view of the LiDARand/or a subset of view for the LiDAR. These methodologies may operatein real-time with the same frame rate of the flash LiDAR sensor, whichenables data playback and Hardware-in-the-Loop (“HiL”) test types.

FIG. 11 illustrates a method for emulating a LiDAR scene for bothsingle-beam and multi-beam flash LiDAR types. The illustrated method mayemulate the entirety of the field of view of a LiDAR systemsimultaneously. The methodology utilizes an optical detector placed infront of a flash LiDAR device. When the LiDAR device outputs it “flash”of light, the detector indicates to the processor of the emulator systemwhen this happens. For single-beam flash LiDAR, only one opticaldetector is utilized to detect the LiDAR flash. For multi-beam flashLiDAR, multiple optical detectors may be used, one for each of the beamsof the LiDAR device. For any LiDARs developed in the future that mightuse scanned or multibeam flash LiDAR with one or multiple beams, adetector that is purpose built to detect which pixels are illuminatedmay be used.

In software, a synthetic point cloud may be created that will be thebasis of what is to be generated back to the LiDAR device once theflash(es) of LiDAR occurs. This synthetic point cloud may include rangeand intensity per point of the point cloud. Those range and intensityvalues are converted to timing and optical intensity values to that maythen be sent back to the emulator for transmission to the LiDAR deviceonce the LiDAR flash(es) occur.

There are two proposed methodologies for accurately generating the pointcloud back to the LiDAR system, illustrated in FIGS. 12 and 13 anddescribed below.

FIG. 12 shows a methodology for generating an emulated Flash PointCloud. This methodology creates a clock with a data rate thatcorresponds to a specific distance resolution. For example, a 1 GHzclock corresponds to a 15 cm distance resolution (e.g., light travelsroughly 30 cm through air in 1 nanosecond, the round trip distance,which corresponds to a 15 cm one-way distance resolution). The clockbreaks the point cloud delays into 15 cm “slices in time and space” andupdates a 2D array with intensity values for each specific instance intime and space. It then populates the next 2D array with the followingslice of time and space, one clock cycle later. Said another way, pointcloud software generates a series of matrices, where each matrixdescribes the array of light intensities to be transmitted back to theLiDAR device at a particular moment in time. Each matrix encodes thelight intensities of the emulated scene at a particular emulateddistance from the LiDAR device. For a 1 GHz clock, the matrices willinstruct a 2D LED array to transmit light back to the LiDAR device witha delay between transmissions of 1 nanosecond, and this delay willemulate progressively larger round-trip delays for subsequent LEDtransmissions. This builds a 3D array of intensities with a smalldistance resolution (15 cm for a 1 GHz clock). Notably, the array willoften have mostly empty elements, since there are very few opticalreturns compared to the distance and timing resolution created by thearray. The system outputs this array responsive to receiving a detectionfrom the optical detector. Timing for outputting the array is calibratedso that the round trip distance of the LiDAR device's output and inputis identical to what it would expect in the “real world,” which meansthere is a minimum distance that the system is capable of emulating.

The optical output of the emulator system is transmitted through adensely packed 2D LED or optical diode, e.g., similar to an OLED screen.Each element of the optical array may be driven at the same clock rateas chosen previously. The 2D LED array may operate in the appropriateoptical spectrum for the specific LiDAR sensor, such as 905 nm. Eachelement of the 2D LED array has variable amplitude control, and theamplitude of each pixel for each successive output is determined bycorresponding values of the elements of the 2D matrices received fromthe point cloud software. These embodiments may utilize large amounts ofmemory space and fairly complex electrical design, but advantageouslyutilize relatively simple optical design.

FIG. 13 illustrates an alternative methodology for generating anemulated scene for flash LiDAR, according to some embodiments. This issimilar to the methodology described in conjunction with FIG. 12 in thatit takes the software output from the emulation software as a series ofdelays and intensities. Where this differs is that each element of the2D LED optical array has its own dedicated timing element, as opposed toutilizing a global 1 GHz clock. Advantageously, this eliminates the needfor creating an array with mostly empty elements. Further, the systemshown in FIG. 13 may effectively operate with a slower (and lessexpensive) 100 MHz clock, rather than the 1 GHz clock used in the systemshown in FIG. 12 . Rather, each pixel has a dedicated module thattransmits instructions to the respective pixel to output light at aspecified intensity. However, the embodiment described in FIG. 13utilizes more electrical and optical complexity than that described inFIG. 12 , since one delay generator and one optical amplifier isutilized per optical element of the 2D array.

FIG. 14 —Flowchart for ToF/FMCW LiDAR Environment Emulation

FIG. 14 is a flowchart diagram illustrating a method for an emulatorsystem to emulate an over-the-air environment for testing a ToF and/orFMCW LiDAR UUT, according to various embodiments. The emulator systemmay include a lens system and a plurality of optical processing chains.The emulator system may further include a processor coupled to anon-transitory memory medium wherein the processor is configured todirect operation of the emulator system. In some embodiments, thedescribed methods and systems may be specifically tailored to operatewith ToF LiDAR UUTs. Alternatively, the described methods and systemsmay be specifically tailored to operate with FMCW LiDAR UUTs, or theymay be adapted such that a single emulator system may operate with bothToF and FMCW LiDAR UUTs.

Aspects of the method of FIG. 14 may be implemented by an emulatorsystem, e.g., such as those illustrated in and described with respect tovarious of the Figures herein, or more generally in conjunction with anyof the computer circuitry, systems, devices, elements, or componentsshown in the above Figures, among others, as desired. For example, aprocessor (and/or other hardware) of such a device may be configured tocause the device to perform any combination of the illustrated methodelements and/or other method elements.

Note that while at least some elements of the method of FIG. 14 aredescribed in a manner relating to the use of techniques and/or featuresassociated with specific LiDAR methodologies, such description is notintended to be limiting to the disclosure, and aspects of the method ofFIG. 14 may be used in any suitable LiDAR system, as desired. In variousembodiments, some of the elements of the methods shown may be performedconcurrently, in a different order than shown, may be substituted for byother method elements, or may be omitted. Additional method elements mayalso be performed as desired. As shown, the method of FIG. 14 mayoperate as follows.

At 1402, a plurality of optical processing chains receives a pluralityof laser pulses from one or more lasers of the LiDAR UUT. Each opticalprocessing chain includes an optical fiber configured to receive adistinct subset of the plurality of laser pulses. In some embodiments,each distinct subset of the plurality of laser pulses includes laserpulses from a distinct laser of the LiDAR UUT, and each laser of theLiDAR UUT sweeps over a distinct portion of the field of view of theLiDAR UUT. In some embodiments, each laser of the plurality of laserssweeps over a single line of the field of view of the LiDAR UUT, and thelens system is configured to focus light received along each line intorespective points. For example, each laser may sweep horizontally in aline, and the lens system may focus each line into a point for receptionby a respective optical fiber. Accordingly, each optical fiber mayreceive a disjoint set of laser pulses from respective lasers of theLiDAR UUT.

At 1404, the received laser pulses are modulated by each of theplurality of optical processing chains. Modulating the received laserpulses may include implementing one or more of in-phase quadrature (IQ)frequency modulation, optical time delays, and/or optical amplitudemodulation. IQ frequency modulation may involve frequency-shifting ortranslating the received laser pulses. Implementing IQ frequencytranslation may be used to emulate Doppler shift and/or time delays forFMCW LiDAR UUTs. Implementing optical time delays may be used to emulatea time-of-flight to objects in the emulated over-the-air environment forToF LiDAR UUTs. Implementing optical amplitude modulation may includeselectively attenuating and/or amplifying the received laser pulses toemulate reflectivity and path loss at locations being emulated in theover-the-air environment. The optical amplitude modulators may includeseparate optical attenuator and amplifier devices, or they may becombined into a single attenuator/amplifier device for each opticalchain. Modulating the received laser pulses is performed to emulate theover-the-air environment. Modulating the received laser pulses may beperformed optically to maintain coherence between the received laserpulses and the modulated laser pulses that are transmitted back to theLiDAR UUT. The plurality of optical processing chains may concurrentlymodulate their respective received laser pulses.

In some embodiments, the emulator system is customized to operatespecifically with ToF LiDAR UUTs. In these embodiments, the opticalprocessing chains may include optical time delays and optical amplitudemodulators, but they may exclude the IQ frequency modulators since ToFLiDAR does not utilize frequency shift information. Alternatively, inother embodiments the emulator system may be customized to operatespecifically with FMCW LiDAR UUTs. In these embodiments, the opticalprocessing chains may include IQ frequency modulators and opticalamplitude modulators, but they may exclude the optical time delays. Forthese embodiments, the IQ frequency translators may be utilized toemulate both Doppler shift and time delay, such that a separate timedelay apparatus is not necessary. For example, for FMCW LiDAR, theplurality of laser pulses each include a linear frequency up-sweepfollowed by a linear frequency down-sweep. Implementing the IQ frequencymodulation may involve shifting the linear frequency up-sweep in a samedirection as the linear frequency down-sweep to emulate a Doppler shiftin the over-the-air environment and shifting the linear frequencyup-sweep in an opposite direction as the linear frequency down-sweep toemulate a time delay in the over-the-air environment.

Alternatively, in some embodiments, the emulator system may include allthree of the IQ frequency modulators, the optical time delays, and theoptical amplitude modulators in each of the optical processing chains.In these embodiments, the emulator system may be programmaticallycontrolled to emulate over-the-air environments for both ToF and FMCWLiDAR UUTs. For example, the emulator system may not activate the IQfrequency modulators when performing emulation for a ToF LiDAR UUT, andit may not activate the optical time delays when performing emulationfor an FMCW LiDAR UUT.

In some embodiments, the emulator system receives frequency modulationvalues, time delay values, and/or amplitude modulation values from aLiDAR image generator for each point in a point cloud of theover-the-air environment. The LiDAR image generator may be a softwareprogram stored on the non-transitory memory medium that is executable bythe processor. The LiDAR image generator may be user programmable toproduce time delay values and amplitude modulation values correspondingto different over-the-air environments. In these embodiments,implementing IQ frequency modulation, optical time delays, and/oroptical amplitude modulation is performed based on the frequencymodulation values, time delay values, and/or the amplitude modulationvalues, respectively.

At 1406, the modulated laser pulses are transmitted to the LiDAR UUT.The modulated laser pulses may be transmitted to the LiDAR UUT throughthe same lens system used to receive the laser pulses from the LiDARUUT, or they may be transmitted through a separate dedicated output lenssystem. For example, each of the optical fibers may be configured totransmit the modulated laser light back through the lens system, forreception by the LiDAR UUT. The LiDAR UUT may then reproduce a LiDARimage based on the received modulated laser light.

FIG. 15 —Flowchart for Flash LiDAR Environment Emulator

FIG. 15 is a flowchart diagram illustrating a method for emulating anover-the-air environment for a flash LiDAR UUT, according to someembodiments. The emulator system may include a processor coupled to anon-transitory memory medium, where the processor is configured todirect operation of the emulator system. The emulator system may furtherinclude one or more optical detectors and a 2D diode array or anothertype of 2D light-emitting array. While embodiments herein describe anemulator system that utilizes a diode or LED array, it may be understoodthat any other type of 2D light-emitting array may also be used and iswithin the scope of some embodiments. In some embodiments, the describedmethods and systems may be specifically tailored to operate with flashLiDAR UUTs.

Aspects of the method of FIG. 15 may be implemented by an emulatorsystem, e.g., such as those illustrated in and described with respect tovarious of the Figures herein, or more generally in conjunction with anyof the computer circuitry, systems, devices, elements, or componentsshown in the above Figures, among others, as desired. For example, aprocessor (and/or other hardware) of such a device may be configured tocause the device to perform any combination of the illustrated methodelements and/or other method elements.

Note that while at least some elements of the method of FIG. 15 aredescribed in a manner relating to the use of techniques and/or featuresassociated with specific LiDAR methodologies, such description is notintended to be limiting to the disclosure, and aspects of the method ofFIG. 15 may be used in any suitable LiDAR system, as desired. In variousembodiments, some of the elements of the methods shown may be performedconcurrently, in a different order than shown, may be substituted for byother method elements, or may be omitted. Additional method elements mayalso be performed as desired. As shown, the method of FIG. 15 mayoperate as follows.

At 1506, one or more optical detectors receive light from the flashLiDAR UUT.

In some embodiments, the flash LiDAR UUT is a multi-flash LiDAR deviceincluding multiple lasers producing multiple respective flashes, whereeach laser flashes light in a different sub-region of the field of view(FoV) of the flash LiDAR UUT. In these embodiments, the emulator systemmay include a plurality of optical detectors, where each opticaldetector of the plurality of optical detectors is configured to receivea flash from a different laser of the multi-flash LiDAR UUT.

At 1502, a processor coupled to a non-transitory computer-readablememory medium generates point cloud information. The point cloudinformation may be generated based on an image of a scene to beemulated, or based on a video including a sequence of frames of a sceneto be emulated. The image or sequence of images may be converted topoint cloud information, where the point cloud information includes adistance, reflectivity, and/or velocity value for each of a plurality ofangular positions (i.e., for a set of angles (θ, φ) spanning the fieldof view of the image at a particular resolution).

At 1504, the point cloud information is converted to delay and amplitudevalues for each point in a 2D array. In some embodiments, as shown inFIG. 12 , the delay and amplitude values are encoded as a plurality ofmatrices corresponding to the emulated over-the-air environment, whereeach matrix of the plurality of matrices corresponds to a differentemulated time delay, and each entry in each matrix of the plurality ofmatrices specifies an amplitude of a pixel of a two-dimensional (2D)light-emitting diode (LED) array. For example, each matrix may presentan intensity map for the pixels of the 2D LED array. Alternatively, inother embodiments the delay and amplitude values are encoded as anemulated flash point cloud that specifies an intensity and/or delay foreach pixel of the 2D LED array, as shown in FIG. 13 .

In some embodiments, the non-transitory computer-readable memory mediumhas stored thereon point cloud information that is generated in softwarethat is user programmable to configure the emulated over-the-airenvironment. The emulated over-the-air environment may specify alocation (e.g., x, y and z coordinates) and a reflectivity for eachpoint in a point cloud, and generating the point cloud information maybe performed by the point cloud software based on the location andreflectivity of each point in the point cloud.

In some embodiments, software may be executed to determine theappropriate delay and amplitude values for each point in the field ofview that corresponds to the point cloud information of the emulatedover-the-air environment. In some embodiments, the delay and amplitudevalues are stored as a series of 2D matrices, where the entries in thematrix correspond to the amplitude of light at different points in thefield of view, and the different matrices each correspond to a differenttime delay. In these embodiments, as described below, the series ofmatrices may be sequentially provided to the 2D light-emitting array tocause the light-emitting array to sequentially emit light according tothe amplitude values and the time delays.

Alternatively, the delay and amplitude values may be organized accordingto their respective pixels, i.e., each pixel may have a correspondingdelay and amplitude value, and these may be provided to separate timingelements for each pixel, to cause the pixels to emit light according totheir respective delay and amplitude values. These embodiments have theadvantage of utilizing a smaller data footprint for the delay andamplitude values compared to the embodiment that utilizes sequentialmatrices as described above. For example, representing the delay andamplitude values as a series of matrices will typically introduce alarge number of null entries. However, an advantage of the sequentialmatrix representation is that a single timing element is used for the 2Ddiode array, rather than assigning a separate timing element for eachpixel.

At 1508, delay and amplitude values are received by the emulator system.The emulator system may provide signaling to the 2D diode array causingthe array to emit light according to the delay and amplitude values. The2D diode array may be a light emitting diode (LED) array, or anothertype of light-emitting array for controllably emitting a plurality ofbeams of light. For an emulator system configured to emulate anenvironment for a multi-flash LiDAR UUT, portions of the converted pointcloud information may be separately provided to the 2D diode arrayresponsive to receiving each flash of the plurality of flashes. Forexample, each received flash may trigger the processor to provide pointcloud information corresponding to the sub-region of the FoV illuminatedby the received flash.

In some embodiments, providing the point cloud information includessequentially providing, by the processor, matrices of the plurality ofmatrices to the 2D diode array. In some embodiments, the matrices of theplurality of matrices are provided to the 2D diode array periodicallywith a predetermined periodicity, where the 2D diode array emits lightto the flash LiDAR UUT with the predetermined periodicity, and where thepredetermined periodicity corresponds to a depth resolution of theemulated over-the-air environment (see, e.g., FIG. 12 ). Each matrixreceived by the 2D diode array may trigger the diode array to emit lightaccording to the intensities specified by the matrix, as describedbelow.

Alternatively, in some embodiments, the processor is coupled to aplurality of timing elements and each timing element is coupled to apixel of the 2D diode array. In these embodiments, the processor maysend, to each timing element, intensity and timing information for thespecific pixel coupled to the respective timing element (see, e.g., FIG.13 ). The timing elements may then transmit the intensity information toits coupled pixel according to the timing information. For example, eachtiming element may separately instruct its coupled pixel to emit asequence of pulses according to the intensity and timing information.

In some embodiments, timing for providing the point cloud information tothe 2D diode array is selected to emulate a round trip time of theemulated over-the-air environment.

In some embodiments, a synchronization clock may be used to synchronizethe one or more optical devices receiving the light from the flash LiDARUUT with the processor providing the matrices of the plurality ofmatrices to the 2D diode array.

At 1510, responsive to receiving the delay and amplitude values, the 2Ddiode array emits a series of light pulses to the flash LiDAR UUTthrough a lens system. For example, when the point cloud information isa series of matrices, each matrix may trigger the 2D diode array to emitlight according to the intensity pattern indicated by the matrix. The 2Ddiode array may receive a sequence of matrices, and may sequentiallyemit light according to the indicated patterns. Alternatively, the delayand amplitude values may be directly provided to a plurality of timingelements that are each coupled to a different pixel of the 2D diodearray, and the timing elements may utilize the delay and amplitudevalues corresponding to their respective pixels to cause the pixels toemit light according to the delay and amplitude values. The lightemitted by the 2D diode array emulates light that would be emitted bythe emulated over-the-air environment responsive to receiving the lightfrom the flash LiDAR UUT. The flash LiDAR may use the light receivedfrom the 2D diode array to produce a LiDAR image, for testing or otherpurposes.

Additional Embodiments

The following are examples of additional aspects of the describedembodiments:

FIG. 6 illustrates a parallel point cloud emulator that is genericenough to work for all LiDAR types, including TOF, FMCW and Flash. Theparallel point cloud emulator may include a high level of integrationand, while expensive, may become more economically viable in the future.

The point cloud emulators for scanned, pulsed systems shown in FIGS.8A-B may work for FMCW as well as TOF. This point cloud emulator may usean optical shutter array. Other advantageous aspects of the systeminclude coupling a photodetector array to an optical shutter arraymapping the photodetector array to the optical shutters in various ways.

The optical IQ modulator may be removed from the parallel point cloudemulators shown in FIGS. 8A-B for exclusive use in TOF LiDAR systems.

An optical IQ modulator and/or an electro-optical PLL (EOPLL) may beused for frequency shifts in various embodiments.

A different frequency shift may be used for the up-slope and thedown-slope of a linear-shift frequency pulse to emulate both distanceand Doppler shift. This enables the removal of the delay generator fromthe parallel point cloud emulators shown in FIGS. 8A-B, to reduce costsfor FMCW LiDAR system scene emulation.

One embodiment relates to a method for generating a point cloud. Themethod for generating a point cloud may receive a description of a scenein the form of a list of points and descriptors, photographs, videofiles and or mathematical formulas and may generate the information fora point cloud. The information for a point cloud may include: Verticalangle, Horizontal angle, Distance, Velocity, and Reflectivity for eachpoint in the point cloud. The method for generating a point cloud allowsfor the introduction of LiDAR impairments such as dust, snow, rain,sunlight, light from other LIDARs, etc.

Another embodiment relates to a method for translating the point cloudinto an array of vertical and horizontal angles, distance, reflectivity,and Doppler shift. The method for translating point clouds into LiDARparameters may include representing: 1) Speed as the appropriate amountof Doppler shift for the light wavelength used; 2) Distance as theappropriate amount of delay; 3) Reflectivity as the appropriate amountof gain or attenuation for any given distance; and 4) Vertical andhorizontal angles as the position on a grid of light emitters or lightshutters.

Therefore, these embodiments may be operable to translate the elementsof a scene into hardware parameters that can be used to emulate thescene. These hardware parameters may then be used in the LiDAR emulatordescribed herein to emulate the scene.

Another embodiment relates to a combined system configured to performLiDAR scene emulation and laser measurements. For example, the systemsdescribed herein may further include a delay line discriminator, opticalphase-locked loop (PLL), optical demodulator, etc. to measure chirplinearity. Another embodiment relates to a method for measuring laserline width (the optical equivalent of jitter or phase noise), opticalpower measurements, or pulse width measurements, among otherpossibilities. Examples of this method include use of an optical PLL, adelay line discriminator, an optical spectrum analyzer. In theseembodiments, the same emulator system used to emulate an over-the-airenvironment may also be configured to perform these measurements onlight received from a LiDAR system. In other words, a single system maybe configured to perform the dual purposes of both LiDAR scene emulationand LiDAR light measurement. Some components of the system may be sharedand used for both scene emulation and light measurement, such as thelens system, optical fibers, and/or one or more interfaces used topower, control, and receive data from the LiDAR unit. The system mayfurther include additional components for performing light measurements.Chirp linearity and laser line width may be used in assessing whetherthe received light is an appropriate candidate for LiDAR emulation asdescribed herein.

In some embodiments, a system is described for emulating an over-the-airenvironment for testing a light detection and ranging (LiDAR) unit undertest. The system comprises a lens system configured to receive lightfrom the LiDAR unit under test, and a plurality of optical processingchains coupled to the lens system. Each of the optical processing chainscomprises at least one optical fiber coupled to the input lens systemand configured to provide optical signals corresponding to the receivedlight; a frequency shift emulator coupled to the plurality of opticalfibers, wherein the frequency shift emulator is configured to create afrequency offset in the received optical signals; a selectable opticaldelay device coupled to the frequency shift estimator and configured toselectively delay the optical signals to emulate a round-trip delay ofreflected light; and/or at least one optical attenuator/amplifierconfigured to control the amplitude of the optical signals to emulatedifferent levels of reflectivity, polarization change, and path lossfrom free space, spectral components of the reflection, and/or diffusecomponents of the reflection. Each optical processing chain isconfigured to output the processed optical signals to the LiDAR unitunder test through the lens system. Alternatively, in some embodimentseach optical processing chain is configured to output the processedoptical signals to the LiDAR UUT through an output lens system(different from the lens system used to receive the light from the LiDARUUT) coupled to each of the optical processing chains and configured togenerate light into free space based on the optical signals processed byeach optical processing chain.

In various embodiments, the frequency shift emulator comprises anoptical IQ modulator or an optical phase-locked loop.

In some embodiments, in each optical processing chain, the at least oneoptical attenuator/amplifier is configured to selectively attenuate oramplify the optical signal to enable the light intensity output by thesystem corresponds to reflectivity and path loss at a location on anobject being emulated.

In some embodiments, the system is configured to process received lightoptically to maintain coherence with light received from the LiDAR unitunder test.

In some embodiments, the system is configured to process all points in aLiDAR image simultaneously.

In some embodiments, the system further comprises a LiDAR imagegenerator coupled to the frequency shift emulator, the selectableoptical delay and the at least one optical attenuator/amplifier. TheLiDAR image generator is user programmable to control operation of thefrequency shift emulator, the selectable optical delay and the at leastone optical attenuator/amplifier.

In some embodiments, the LiDAR image generator is configured to providea frequency shift value to the frequency shift emulator for use by thefrequency shift emulator in creating a frequency offset in the receivedoptical signals.

In some embodiments, the LiDAR image generator is configured to providea delay value to the selectable optical delay for use by the selectableoptical delay to delay the optical signals to emulate a round-trip delayof reflected light

In some embodiments, the LiDAR image generator is configured to providean amplitude value to the at least one optical attenuator/amplifier foruse by the optical attenuator/amplifier to control the amplitude of theoptical signals to emulate different levels of reflectivity,polarization change, and path loss from free space, spectral componentsof the reflection, and/or diffuse components of the reflection.

In some embodiments, the LiDAR image generator is configured to providethe frequency shift value, the delay value, and the amplitude value foreach point in a point cloud generated by the system.

In some embodiments, the frequency shift emulator is configured to use adifferent frequency shift for up-slope and down-slope to emulate bothdistance and Doppler shift.

In some embodiments, a system is described for emulating an over-the-airenvironment for testing a LiDAR UUT. The system comprises an input lenssystem configured to receive light from the LiDAR UUT; an input opticalsplitting block coupled to the input lens system and configured toreceive optical signals and provide portions of the optical signals to afirst optical processing path and a second optical processing path; andat least one optical shutter array coupled to the first opticalprocessing path and the second optical processing path. Alternatively,in some embodiments the optical shutter array is removed and a lenssystem is be used to both receive the light from the LiDAR UUT andoutput the processed light back to the LiDAR UUT. The first opticalprocessing path comprises an array of photodetectors for determiningangles of the laser pulse at a particular instant in time, wherein alocation of received light on the photodetector array is used to open acorresponding element in the optical shutter array. The second opticalprocessing path comprises an amplitude controller configured to controlamplitude of the optical signals to emulate different levels ofreflectivity and path loss and a LiDAR image generator coupled to theamplitude controller. The second optical processing path is configuredto provide an attenuated signal to the at least one optical shutterarray or lens system for exit through one or more open elements in theoptical shutter array or through the lens system.

In some embodiments, a location of received light on the photodetectorarray corresponds to a vertical and horizontal scanning angle (ϕ,θ),wherein the vertical and horizontal scanning angle is used to open acorresponding element in the optical shutter array.

In some embodiments, the second optical processing path furthercomprises a frequency shifter coupled to the selectable optical delayelement, wherein the frequency shifter is configured to create afrequency offset in the received optical signals. In some embodiments,the second optical processing path is configured to provide a frequencyshifted and attenuated signal to the at least one optical shutter arrayor lens system for exit through one or more open elements in the opticalshutter array or lens system.

In some embodiments, the second optical processing path furthercomprises a selectable optical delay element coupled to the frequencyshifter, wherein the selectable optical delay element is configured toselectively delay the optical signals to emulate a round-trip delay ofreflected light. The second optical processing path is configured toprovide a delayed and attenuated signal to the at least one opticalshutter array or lens system for exit through one or more open elementsin the optical shutter array or lens system.

In some embodiments, the second optical processing path furthercomprises a frequency shifter coupled to the selectable optical delayelement, wherein the frequency shifter is configured to create afrequency offset in the received optical signals; and a selectableoptical delay element coupled to the frequency shifter, wherein theselectable optical delay element is configured to selectively delay theoptical signals to emulate a round-trip delay of reflected light. Thesecond optical processing path is configured to provide a delayed,frequency shifted and attenuated signal to the at least one opticalshutter array or lens system for exit through one or more open elementsin the optical shutter array or lens system.

In some embodiments, each photodetector in the array of photodetectorshas a one-to-one mapping with a corresponding shutter in the opticalshutter array.

In some embodiments, each of a plurality of sets of pluralphotodetectors in the array of photodetectors has a many-to-one mappingwith a corresponding shutter in the optical shutter array.

In some embodiments, a system is described for emulating an over-the-airenvironment for testing a LiDAR UUT. The system comprises an input lenssystem configured to receive light from the LiDAR UUT, an input opticalsplitting block coupled to the input lens system and configured toreceive optical signals and provide portions of the optical signals to afirst optical processing path and a second optical processing path, andat least one optical shutter array coupled to the first opticalprocessing path and the second optical processing path. The firstoptical processing path comprises an array of photodetectors fordetermining angles (ϕ,θ) of the laser pulse at a particular instant intime, wherein a location of received light on the photodetector array isused to open a corresponding element in the optical shutter array. Thesecond optical processing path comprises a selectable optical delayelement coupled to the frequency shifter and configured to selectivelydelay the optical signals to emulate a round-trip delay of reflectedlight; an amplitude controller coupled to the selectable optical delayelement to control the amplitude of the optical signals to emulatedifferent levels of reflectivity and path loss; and a LiDAR imagegenerator coupled to the selectable optical delay element and theamplitude controller. The second optical processing path is configuredto provide a delayed, Doppler shifted and attenuated signal to the atleast one optical shutter array for exit through one or more openelements in the optical shutter array.

In some embodiments, a method is described for converting a descriptionof a scene into LiDAR parameters. The method comprises receiving adescription of a scene in the form of two or more of points anddescriptors, photographs, video files and/or mathematical formulas; andgenerating the information for a point cloud based on the receiveddescription. The information for the point cloud includes verticalangle, horizontal angle, distance, velocity, and reflectivity. Themethod for generating a point cloud allows for the introduction of LiDARimpairments into an emulation. The method further comprises translatingthe point cloud into LiDAR parameters, wherein the LiDAR parametersinclude an array of vertical and horizontal angles, distance,reflectivity, and Doppler shift.

In some embodiments, the method for translating point clouds into LiDARparameters may include representing: 1) speed as an appropriate amountof Doppler shift for light wavelength used; 2) distance as anappropriate amount of delay; 3) reflectivity as the appropriate amountof gain or attenuation for the at any given distance; and/or 4) verticaland horizontal angles as the position on a grid of light emitters orlight shutters.

The following numbered paragraphs describe additional embodiments.

In some embodiments, systems and methods are described for emulating anover-the-air environment for testing a light detection and ranging(LiDAR) unit under test (UUT). The method includes receiving, by aplurality of optical processing chains, a plurality of laser pulses fromone or more lasers of the LiDAR UUT, wherein each optical processingchain comprises an optical fiber configured to receive a distinct subsetof the plurality of laser pulses; for each of the optical processingchains, modulating the received laser pulses by implementing in-phasequadrature (IQ) frequency modulation, optical time delays, and/oroptical amplitude modulation; and transmitting the modulated laserpulses to the LiDAR UUT.

In some embodiments, modulating the received laser pulses is performedto emulate the over-the-air environment.

In some embodiments, the LiDAR UUT comprises a frequency modulatedcontinuous wave (FMCW) LiDAR UUT.

In some embodiments, the plurality of laser pulses comprise a linearfrequency up-sweep followed by a linear frequency down-sweep, andimplementing the IQ frequency modulation comprises shifting the linearfrequency up-sweep in a same direction as the linear frequencydown-sweep to emulate a Doppler shift in the over-the-air environment;and shifting the linear frequency up-sweep in an opposite direction asthe linear frequency down-sweep to emulate a time delay in theover-the-air environment.

In some embodiments, each distinct subset of the plurality of laserpulses comprises laser pulses from a distinct laser of the LiDAR UUT,wherein each laser of the LiDAR UUT sweeps over a distinct portion ofthe field of view of the LiDAR UUT.

In some embodiments, implementing optical amplitude modulation comprisesselectively attenuating and/or amplifying the received laser pulses toemulate reflectivity and path loss at locations being emulated in theover-the-air environment.

In some embodiments, modulating the received laser pulses is performedoptically to maintain coherence between the received laser pulses andthe modulated laser pulses.

In some embodiments, the plurality of optical processing chainsconcurrently modulate their respective received laser pulses.

In some embodiments, the method further comprises receiving frequencymodulation values and amplitude modulation values from a LiDAR imagegenerator for each point in a point cloud of the over-the-airenvironment, wherein said implementing IQ frequency modulation andoptical amplitude modulation is performed based on the frequencymodulation values and the amplitude modulation values.

In some embodiments, a system for emulating an over-the-air environmentfor testing a light detection and ranging (LiDAR) unit under test (UUT),the system comprises a lens system configured to receive light from theLiDAR UUT; a plurality of optical processing chains coupled to the lenssystem, wherein each optical processing chain comprises: an opticalfiber coupled to the lens system and configured to receive laser pulsesfrom the LiDAR UUT through the lens system; an in-phase quadrature (IQ)frequency modulator configured to modulate a frequency of the receivedlaser pulses; an optical time delay configured to time delay thereceived laser pulses; and an optical amplitude modulator configured tomodulate an amplitude of the received laser pulses. Each opticalprocessing chain is configured to transmit the frequency shifted, timedelayed and amplitude modulated laser pulses to the LiDAR UUT.

In some embodiments, the system is further configured to perform one ormore measurements on light received from the LiDAR UUT, wherein the oneor more measurements comprise one or more of a laser line widthmeasurement, a chirp linearity measurement, an optical spectrum analyzermeasurement, an optical power measurement, and a pulse widthmeasurement.

In some embodiments, the LiDAR UUT comprises a frequency modulatedcontinuous wave (FMCW) LiDAR UUT.

In some embodiments, the received laser pulses comprise a linearfrequency up-sweep followed by a linear frequency down-sweep, whereinmodulating the frequency of the received laser pulses comprises shiftingthe linear frequency up-sweep in a same direction as the linearfrequency down-sweep to emulate a Doppler shift in the over-the-airenvironment.

In some embodiments, each optical fiber receives a distinct subset oflaser pulses received from a distinct laser of a plurality of lasers ofthe LiDAR UUT, wherein each laser of the plurality of lasers sweeps overa distinct portion of the field of view of the LiDAR UUT.

In some embodiments, each laser of the plurality of lasers sweeps over asingle line of the field of view of the LiDAR UUT, and wherein the lenssystem is configured to focus light received along each line intorespective points.

In some embodiments, modulating the amplitude of the received laserpulses comprises selectively attenuating and/or amplifying the receivedlaser pulses to emulate reflectivity and path loss at a locations beingemulated in the over-the-air environment.

In some embodiments, delaying and modulating the frequency and theamplitude and of the received laser pulses is performed optically tomaintain coherence between the received laser pulses and the modulatedlaser pulses.

In some embodiments, the plurality of optical processing chainsconcurrently modulate their respective received laser pulses.

In some embodiments, the system further comprises a LiDAR imagegenerator coupled to the plurality of optical processing chains, whereinthe LiDAR image generator is configured to provide frequency modulation,time delay and amplitude modulation values to the plurality of opticalprocessing chains for each point in a point cloud of the over-the-airenvironment, wherein the LiDAR image generator is user programmable toproduce frequency modulation, time delay and amplitude modulation valuescorresponding to different over-the-air environments, and whereindelaying and modulating the frequency and amplitude of the receivedlaser pulses is performed based on the frequency modulation, time delay,and amplitude modulation values.

In some embodiments, the frequency shifted, time delayed and amplitudemodulated laser pulses are transmitted to the LiDAR UUT through the lenssystem.

In some embodiments, systems and methods are described for emulating anover-the-air environment for testing a light detection and ranging(LiDAR) unit under test (UUT), the method comprising: receiving, by aplurality of optical processing chains, a plurality of laser pulses fromone or more lasers of the LiDAR UUT, wherein each optical processingchain comprises an optical fiber configured to receive a distinct subsetof the plurality of laser pulses; for each of the optical processingchains, modulating the received laser pulses by implementing: opticaltime delays; and optical amplitude modulation; and transmitting themodulated laser pulses to the LiDAR UUT.

In some embodiments, modulating the received laser pulses is performedto emulate the over-the-air environment.

In some embodiments, the LiDAR UUT comprises a time-of-flight (ToF)LiDAR UUT.

In some embodiments, implementing optical time delays emulates atime-of-flight to objects in the emulated over-the-air environment.

In some embodiments, each distinct subset of the plurality of laserpulses comprises laser pulses from a distinct laser of the LiDAR UUT,and each laser of the LiDAR UUT sweeps over a distinct portion of thefield of view of the LiDAR UUT.

In some embodiments, implementing optical amplitude modulation comprisesselectively attenuating and/or amplifying the received laser pulses toemulate reflectivity and path loss at locations being emulated in theover-the-air environment.

In some embodiments, modulating the received laser pulses is performedoptically to maintain coherence between the received laser pulses andthe modulated laser pulses.

In some embodiments, the plurality of optical processing chainsconcurrently modulate their respective received laser pulses.

In some embodiments, the method further includes receiving time delayvalues and amplitude modulation values from a LiDAR image generator foreach point in a point cloud of the over-the-air environment, where saidimplementing optical time delays and optical amplitude modulation isperformed based on the time delay values and the amplitude modulationvalues.

In some embodiments, the plurality of laser pulses are received from theLiDAR UUT and the modulated laser pulses are transmitted to the LiDARUUT through a lens system.

In some embodiments, a system for emulating an over-the-air environmentfor testing a light detection and ranging (LiDAR) unit under test (UUT),includes a lens system configured to receive light from the LiDAR UUTand a plurality of optical processing chains coupled to the lens system.Each optical processing chain includes an optical fiber coupled to thelens system and configured to receive laser pulses from the LiDAR UUTthrough the lens system, a selectable optical delay device configured toselectively delay the received laser pulses; and an optical amplitudemodulator configured to modulate an amplitude of the received laserpulses. Each optical processing chain is configured to transmit theselectively delayed and amplitude modulated laser pulses to the LiDARUUT.

In some embodiments, the system is further configured to perform one ormore measurements on light received from the LiDAR UUT, wherein the oneor more measurements comprise one or more of a laser line widthmeasurement, a chirp linearity measurement, an optical spectrum analyzermeasurement, an optical power measurement, and a pulse widthmeasurement.

In some embodiments, the LiDAR UUT comprises a time-of-flight (ToF)LiDAR UUT.

In some embodiments, each of the plurality of optical processing chainsfurther comprises an in-phase quadrature (IQ) frequency modulatorconfigured to modulate a frequency of the received laser pulses, whereinthe system is configured to emulate the over-the-air environment foreither a time-of-flight (ToF) LiDAR UUT or a frequency modulatedcontinuous wave (FMCW) LiDAR UUT, wherein the selectable optical delaydevices are utilized to emulate over-the-air environments for ToF LiDARUUTs, and wherein the IQ frequency modulators are utilized to emulateover-the-air environments for FMCW LiDAR UUTs.

In some embodiments, each optical fiber receives a distinct subset oflaser pulses received from a distinct laser of a plurality of lasers ofthe LiDAR UUT, and each laser of the plurality of lasers sweeps over adistinct portion of the field of view of the LiDAR UUT.

In some embodiments, each laser of the plurality of lasers sweeps over asingle line of the field of view of the LiDAR UUT, and the lens systemis configured to focus light received along each line into respectivepoints.

In some embodiments, modulating the amplitude of the received laserpulses comprises selectively attenuating and/or amplifying the receivedlaser pulses to emulate reflectivity and path loss at locations beingemulated in the over-the-air environment.

In some embodiments, selectively delaying and modulating the amplitudeof the received laser pulses is performed optically to maintaincoherence between the received laser pulses and the modulated laserpulses.

In some embodiments, the system further includes a LiDAR image generatorcoupled to the plurality of optical processing chains, wherein the LiDARimage generator is configured to provide time delay values and amplitudemodulation values to the plurality of optical processing chains for eachpoint in a point cloud of the over-the-air environment, wherein theLiDAR image generator is user programmable to produce time delay valuesand amplitude modulation values corresponding to different over-the-airenvironments, and wherein selectively delaying and modulating theamplitude of the received laser pulses is performed based on the timedelay values and the amplitude modulation values.

In some embodiments, the frequency shifted and amplitude modulated laserpulses are transmitted to the LiDAR UUT through the lens system.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

We claim:
 1. A system for emulating an over-the-air environment fortesting a flash light detection and ranging (LiDAR) unit under test(UUT), the system comprising: a processor coupled to a non-transitorycomputer-readable memory medium; one or more optical detectors; atwo-dimensional (2D) light-emitting array, wherein the system isconfigured to: receive, by the one or more optical detectors, light fromthe flash LiDAR UUT; generate, by the processor, a plurality of matricescorresponding to the emulated over-the-air environment, wherein eachmatrix of the plurality of matrices corresponds to a different emulatedtime delay, wherein each entry in each matrix of the plurality ofmatrices specifies an amplitude of a pixel of the 2D light-emittingarray; responsive to receiving the light by the one or more opticaldetectors, sequentially provide, by the processor, matrices of theplurality of matrices to the 2D light-emitting array, wherein eachprovided matrix causes the 2D light-emitting array to emit light to theflash LiDAR UUT through a lens according to the specified amplitudes. 2.The system of claim 1, wherein the light emitted by the 2Dlight-emitting array emulates light that would be emitted by theemulated over-the-air environment responsive to receiving the light fromthe flash LiDAR UUT.
 3. The system of claim 1, wherein the flash LiDARUUT comprises a multi-flash LiDAR device, wherein the light from theflash LiDAR UUT comprises a plurality of flashes in different regions ofa field of view of the flash LiDAR UUT from different respective lasersof the multi-flash LiDAR device, and wherein the one or more opticaldetectors comprises a plurality of optical detectors, wherein eachoptical detector of the plurality of optical detectors is configured toreceive a different flash of the plurality of flashes.
 4. The system ofclaim 3, wherein sequentially providing matrices of the plurality ofmatrices to the 2D light-emitting array is separately performedresponsive to receiving each flash of the plurality of flashes.
 5. Thesystem of claim 1, wherein the matrices of the plurality of matrices areprovided to the 2D light-emitting array periodically with apredetermined periodicity, wherein the 2D light-emitting array emitslight to the flash LiDAR UUT with the predetermined periodicity, andwherein the predetermined periodicity corresponds to a depth resolutionof the emulated over-the-air environment.
 6. The system of claim 1,wherein the system is further configured to: perform one or moremeasurements on light received from the LiDAR UUT, wherein the one ormore measurements comprise one or more of: a laser line widthmeasurement; a chirp linearity measurement; an optical spectrum analyzermeasurement; an optical power measurement; and a pulse widthmeasurement.
 7. The system of claim 1, the system further comprising:point cloud software stored on the non-transitory computer-readablememory medium, wherein the point cloud software is executable by theprocessor, wherein the point cloud software is user programmable toconfigure the emulated over-the-air environment, wherein the emulatedover-the-air environment comprises a location and a reflectivity foreach point in a point cloud, and wherein the point cloud software isconfigured to generate the plurality of matrices based on the locationand reflectivity of each point in the point cloud.
 8. The system ofclaim 1, the system further comprising: a synchronization clockconfigured to synchronize the one or more optical devices receiving thelight from the flash LiDAR UUT with the processor providing the matricesof the plurality of matrices to the 2D light-emitting array.
 9. A methodfor emulating an over-the-air environment for testing a flash lightdetection and ranging (LiDAR) unit under test (UUT), the methodcomprising: receiving, by one or more optical detectors, light from theflash LiDAR UUT; generating, by a processor coupled to a non-transitorycomputer-readable memory medium, a plurality of matrices correspondingto the emulated over-the-air environment, wherein each matrix of theplurality of matrices corresponds to a different emulated time delay,wherein each entry in each matrix of the plurality of matrices specifiesan amplitude of a pixel of a two-dimensional (2D) light-emitting array;responsive to receiving the light by the one or more optical detectors,sequentially providing, by the processor, matrices of the plurality ofmatrices to the 2D light-emitting array, responsive to receiving eachmatrix of the plurality of matrices, emitting, by the 2D light-emittingarray, light to the flash LiDAR UUT through a lens according to thespecified amplitudes.
 10. The method of claim 9, wherein the 2D lightemitting array comprises a 2D light-emitting diode (LED) array.
 11. Themethod of claim 9, wherein the flash LiDAR UUT comprises a multi-flashLiDAR device, wherein the light from the flash LiDAR UUT comprises aplurality of flashes in different regions of a field of view of theflash LiDAR UUT from different respective lasers of the multi-flashLiDAR device, and wherein the one or more optical detectors comprises aplurality of optical detectors, wherein each optical detector of theplurality of optical detectors receives a different flash of theplurality of flashes.
 12. The method of claim 11, wherein sequentiallyproviding matrices of the plurality of matrices to the 2D light-emittingarray is separately performed responsive to receiving each flash of theplurality of flashes.
 13. The method of claim 9, wherein the matrices ofthe plurality of matrices are provided to the 2D light-emitting arrayperiodically with a predetermined periodicity, wherein the 2Dlight-emitting array emits light to the flash LiDAR UUT with thepredetermined periodicity, and wherein the predetermined periodicitycorresponds to a depth resolution of the emulated over-the-airenvironment.
 14. The method of claim 9, the method further comprising:selecting a timing for providing the matrices to the 2D light-emittingarray to emulate a round trip time of the emulated over-the-airenvironment.
 15. The method of claim 9, wherein the non-transitorycomputer-readable memory medium has stored thereon point cloud software,wherein the point cloud software is user programmable to configure theemulated over-the-air environment, wherein the emulated over-the-airenvironment comprises a location and a reflectivity for each point in apoint cloud, and wherein generating the plurality of matrices isperformed by the point cloud software based on the location andreflectivity of each point in the point cloud.
 16. The method of claim9, the method further comprising: synchronizing, by a synchronizationclock, the one or more optical devices receiving the light from theflash LiDAR UUT with the processor providing the matrices of theplurality of matrices to the 2D light-emitting array.
 17. A system foremulating an over-the-air environment for testing a flash lightdetection and ranging (LiDAR) unit under test (UUT), the systemcomprising: a processor coupled to a non-transitory computer-readablememory medium; one or more optical detectors; a plurality of timingelements; a two-dimensional (2D) light-emitting array, wherein eachpixel of the 2D light-emitting array is coupled to a different timingelement, wherein the system is configured to: receive, by the one ormore optical detectors, light from the flash LiDAR UUT; generate, by theprocessor, an emulated flash point cloud, wherein the emulated flashpoint cloud specifies an intensity of each pixel of the 2Dlight-emitting array for a plurality of instances in time; responsive toreceiving the light, provide, by the processor, the emulated flash pointcloud to the plurality of timing elements; and by each timing element,trigger the pixel of the 2D light-emitting array coupled to therespective timing element to emit light to the flash LiDAR UUT through alens according to the specified intensities at each of the plurality ofinstances in time.
 18. The system of claim 17, wherein the light emittedby the pixels of the 2D light-emitting array emulates light that wouldbe emitted by the emulated over-the-air environment responsive toreceiving the light from the flash LiDAR UUT.
 19. The system of claim17, wherein providing the emulated flash point cloud to the plurality oftiming elements comprises providing, to each timing element of theplurality of timing elements, specified intensities and correspondingspecified instances in time for the pixel of the 2D light-emitting arraycoupled to the respective timing element.
 20. The system of claim 17,wherein the flash LiDAR UUT comprises a multi-flash LiDAR device,wherein the light from the flash LiDAR UUT comprises a plurality offlashes in different regions of a field of view of the flash LiDAR UUTfrom different respective lasers of the multi-flash LiDAR device,wherein the one or more optical detectors comprises a plurality ofoptical detectors, wherein each optical detector of the plurality ofoptical detectors is configured to receive a different flash of theplurality of flashes, and wherein providing the emulated flash pointcloud to the plurality of timing elements is separately performedresponsive to receiving each flash of the plurality of flashes.